Computer freezing and crashing please help!

My pc was running fine until a few weeks ago, and now whenever i play any demanding games such as battlefield 2, or world of warcraft my pc swtiches off entirely or freezes. I don't know why this is, i installed new drivers for my graphics card in the last 2 weeks or so, and i reverted to my original settings.

I have numerous errors in my application event viewer such as:

The source of these two errors is :crypt32
Failed auto update retrieval of third-party root list sequence number from: <http://www.download.windowsupdate.com/msdownload/update/v3/static/trustedr/en/authrootseq.txt> with error: 0x8ca

The source of this error is :ccEvtMgr
The description for Event ID ( 13 ) in Source ( ccEvtMgr ) cannot be found. The local computer may not have the necessary registry information or message DLL files to display messages from a remote computer. You may be able to use the /AUXSOURCE= flag to retrieve this description; see Help and Support for details. The following information is part of the event: ccEvtMgr: Failed to load the configuration settings.

It runs fine when running not very demanding programs such as MSN messenger, or microsoft word, but when i play any sort of game it crashes, even if i play something so basic as football manager, or doom.

I would appreciate any help, as my pc is rendered useles until i solve this problem. Thanks for reading my thread and i await your replies.